The invention relates to a window bonding station for an envelope machine, in other words, to an apparatus for bonding prefabricated cut-to-size window pieces consisting of transparent window material to envelope blanks having window cut-outs.
The cut-to-size window pieces are separated from a web consisting of window material and joined to the envelope blanks with the aid of adhesive. A distinction is made here between two different and fundamentally known concepts. The adhesive may either be applied to the envelope blanks or to the uncut web of window material, from which the cut-to-size window pieces are subsequently separated. The parts provided with adhesive in each case are then fed to a bonding cylinder designed as a suction roller and there joined to the parts having no adhesive.
The web consisting of transparent window material runs, in principle, more slowly than the paper web for the envelope blanks. The cut-to-size window pieces are smaller and shorter in the direction of conveyance than the cut-to-size pieces for the envelope blanks, so that the cut-to-size window pieces have to be accelerated to the speed of the envelope blanks before joining.
It is also necessary to control these different speeds within close tolerances, since otherwise the cut-to-size window pieces will not align exactly with the window cut-outs in the envelope blanks. A final requirement is that the joining station at which the window material is laid on the envelope blank and joined with the aid of adhesive is as large as possible in area and not linear.
It is therefore an object of the invention to provide measures whereby the said difficulties can be controlled more easily than previously. In addition, a compact structure of the apparatus is desired.
To achieve this object, the invention provides a suction belt conveyor device, at least in the region of the joining station or location, as a carrier for the envelope blanks and as a counter-tool for the suction roller serving as an adhesive bonding cylinder.
A suction belt conveyor device with one or more suction belts forms, as a counter-tool for the bonding cylinder, a much larger contact surface than, for example, a counter-roller. Conveyor belts can in principle adapt to a cylindrical contour of a bonding cylinder and are therefore able to generate a contact surface which is much greater than a merely linear joining station.
In a further development of the invention, it is also envisaged that the conveyor belt or belts are moved in an arcuate manner in the region of the suction roller serving as a bonding cylinder. In this case, the conveyor belt or belts are diverted at least partially into a trough at the contact station. The effect of this is to guarantee that the cut-to-size window pieces consisting of window material and the envelope blanks enter into a reliable adhesive bond with one another.